I have a coursemaster cm950 autopilot with gyro compass and rudder feedback unit which behaves erratically when sailing.
So I have been testing.Compass seems ok. Rudder feedback is calibrated. Rudder reads correct on autopilot display.

BUT WHATS GOING ON HERE?

Tied up in the marina on a calm day.
Set the rudders to centre manually and turn on pilot. Pilot keeps rudders in centre.

Set the rudders 4 or so degrees off center to say port then turn on pilot. Pilot drives rudders 4 degrees to starb.
Leave rudders to starb Turn pilot to standby and then turn on, pilot then drives rudders 4 degrees to port. ???

Probably the rate factor is set to high, or possibly something to do with auto tack, best do a cold reset (look up in instructions which are available online). If this fails ring Coursemaster in Chatswood NSW and talk to Jacques

If you can't get it to work you should convert your system to a free autopilot. You can run free software pypilot marine autopilot. I'm adding experimental automatic learning support and much more all the time.

By adjusting the compass deviation I had it working some times quite well. Usually it goes off a few degrees when you go to pilot. But then later in the day off it goes and wants to go off 10 or 20 degrees.

Actually a cold reset is a good idea. I have been fiddling with so much it is worth trying in case I have confused it.

These difficulties weren't a one-off. There were three of us who bought and fitted these pilots around the same time. We all had problems, one was actually worse than mine, the AP just switching itself to standby with no notification.

Some of the conversations with Cursemaster actually beggared belief. One where they seemed to not know the difference between true and apparent wind, for instance .

But the best was a friend who was asked what software version displayed on the screen on startup. It's 3 numbers, and he told them,

"abc".

"No, thats not right, it should be xyz"

"Well it shows abc"

"It can't be abc, it's xyz"

"Mate, I can read 3 numbers, it says abc."

"Are you sure it doesn't say xyz, it really shouldn't
be abc"

And so on...

The amazing thing is they told each one of us that we were the only one having problems. And yet one day Alan Lucas came aboard, and the first thing he said was "Oh no, a Cursemaster! We had one of them, threw it in the bin!".